my picture is just grey and white
It looks like you haven't added a material to your model. You need to add a material, create an image texture node referencing your texture, and connect it to the base_color of the Principled BSDF that appears.

The material can be added by clicking on the +New button above the shader editor (while the mesh is selected), or in the materials tab of the properties panel (on the right, its icon looks like a checkered sphere). You can add the image texture node by pressing shift-a and choosing texture>image texture.

If you want a shadeless texture in EEVEE, use the Emission BSDF node from the shift-a>shader menu.